Three views have dominated the history of scriptural study regarding the nature of man. They are Trichotomy, Dichotomy, and Psychosomatic Unity. Here is a short summary and Biblical evaluation of each position.
The Bible teaches that the Lord took the dust of the ground and created man. The Lord imposed breath within man, and man as a unit became a living soul.
Ancient Greek philosophy insisted upon a distinction between the physical and the spiritual. The physical world, they claimed, was inferior and the physical body was the prison of the soul. The spiritual realm was the reality, and the physical world was a shadow of that reality. Juxtaposed against this, the Bible teaches that the physical world, body included, was created good. Instead of establishing an antithesis between the physical and the spiritual realms, the Bible describes the harmony of the two.
An examination of the words utilized by Biblical writers demonstrates that man is a unitary being. The four primary words used in this context are soul, spirit, heart, and body. A Biblical lexicon reveals that the words used to describe the constitution of man overlap in meaning. Each of these four important terms is used in a way that can only be described as referring to the whole person. These terms refer to the unity of the individual with an emphasis on a particular perspective.
Trichotomy is the view that says the constitution of man consists in three parts or components. Historically, these have been presented as body, soul, and spirit. The body is said to be the external or the physical/material component of man. The Trichotomists believe that Scripture describes two additional components of man's constitution. They say this three-fold idea is presented in both 1 Thessalonians 5:23 and Hebrews 4:12. They argue that both of these verses use "soul" and "spirit" in the same context, thus demonstrating that they are seen as different components of man. They say if this were not the case, there would be no need to employ both terms. The soul is the component of man that includes the life and the will. This is the vitalizing or the "animal life" within the person of man. The spirit, on the other hand, is the organ of God-consciousness in man. The nature of man was created with all three components, but the fall of man resulted in the death of the spirit in man. With the God-consciousness part of man no longer functioning, unregenerate man is seriously lacking in his person. However, the other components, the physical and the soul, which includes the will, continue.
An integral aspect of Trichotomist view is that of components within the nature of man. In order for this view to stand up against scrutiny, it must be able to defend the proposition that the constitution of man is a composite of three separate parts. Scripture does not support the view of man as a three component being. This denies the fundamental presentation of man as a unitary whole and, in many respects, bears resemblance to Greek mythology.
Scripture does not support the Trichotomist emphasis upon the separation of soul and spirit. The insistence that the soul is referred to as the life in man while the spirit is the organ of God-consciousness is pure conjecture that is refuted by objective exegetical and analytical examination. The terms "soul" and "spirit" are virtually synonymous in Biblical theology.
Regarding the fall of man, Biblical theology stands in contrast to the Trichotomist view. Whereas the Trichotomist believe that particular parts of man escape untouched by the fall into sin and the curse of God, Scripture clearly teaches that after the fall, man retained the image of God yet was totally depraved in all his capacities.
The Trichotomist interpretation of 1Thessalonians and Hebrews must be rejected for the following reasons: a.) Systematic study of Biblical theology. The Scriptures should be viewed as a whole and in harmony with all of its individual parts and without contradictions. b.) Context of the verses in question. A basic rule of Biblical hermeneutics is an examination of the context in which any verse is found. To ignore the context is to ignore the intention of the original author. Neither of these texts deal with the constitution of man. The author of Hebrews is emphasizing that the word of the Lord cuts into the very core of our person revealing even the motives behind our actions. The author of 1Thessalonians is emphasizing the sanctification of the entire person. c.) Linguistic study. An understanding of how the key terms are used is vital to proper exegesis. An objective study of the words in question can only lead to the conclusion that, at most, a reference is being made to a particular aspect of the entire person. However, in no way can the words be forced into a proof for a three-component view of the constitution of man. d.) If these verses were to be interpreted in this manner, it would not prove a Trichotomist position. This type of interpretation, if consistent, would lead to many other components of man. For example, Christ taught His followers that they should love the Lord with all their soul, strength, and mind. How many parts would the composite human have when this type of exegesis was consistently performed?
The second position is Dichotomy, the view that the constitution of man consists of two separate components. Historically these have been presented as body and soul. Dichotomists correctly reject the view that the spirit and the soul are separate components of man. They interpret the Scriptures as teaching that man is a composite of both the physical and the spiritual. The dichotomist position is in error in assuming that man is made of two separate components and is subject to the same criticism presented above.
The third position is that of Psychosomatic Unity, the view that the constitution of man consists of a single or unitary constitution that cannot be separated into components. This single unity consists of two inseparable aspects, namely body and spirit, which eternally coincide in the nature of man. The strength of this argument is its faithfulness to systematic theology, linguistic analysis, and overall adherence to both the description and limitation of the Biblical position. The Scriptures describe the constitution of man as being a unit, however, no mechanical explanation is offered or viewed as necessary.
The most significant objection suggested against psychosomatic unity is that of the intermediate state. It is argued that since the Bible describes a period of time in which the spirit exists independent of the physical body, the spirit is properly viewed as a separate component. In response the following can be said: a.) Separation is the exception, not the rule. The constitution of man was created as a unity, in this life continues as a unity, and then after the resurrection will be a unity again. The general principle regarding the nature of man is unity. b.) Separation is a consequence of sin, not the normative for the human constitution. The reason for the separation is the result of the curse of God. Had mankind lived in harmonious obedience to the Lord, the constitution of man would never have experienced the consequence of separation either of the body or the various other results of the fall. This separation should be viewed as a deformity resulting from sin but not as the God given nature of man. c.) Separation will eternally cease. Although, a temporary separation does occur, it will come to a definite end on the day of resurrection when every individual great and small will stand before the throne of the risen Christ to be judged for every thought, word, and deed that has been done in the unity of their person. Then all notions of separation will cease for eternity. After millions of billion years on to infinity have passed away, the constitution of man can hardly be based upon a short deformation of the human nature.
Viewing man as a psychosomatic unity results in a Biblically balanced perspective regarding the nature of man and the work of God in and through him. Seen as a unit, it must be concluded that all aspects of man have been equally created good, affected by the fall, and are currently being sanctified. Furthermore, the relationship between psychosomatic man and his God cannot be reduced to an inward spiritual experience exclusively, but rather must extend to every facet of man's existence. Consequently, any view of man that leads to the conclusion that the body is the prison house of the soul, that man's responsibility toward God is confined to spiritual piety only, or that the sanctification of men and the outworking of the Kingdom of God on earth extends to the spiritual realm exclusively have misrepresented the Biblical view and reveal extra-scriptural influences. The scriptural doctrine of the nature of man is that of psychosomatic unity which necessarily includes the influence of the exterior world in the process of the sanctification of individuals. Such a process will inevitably have significant impact upon every sphere of existence throughout the world as the Kingdom of our Lord goes victoriously forward.